An image sensor is a part for photographing images in a portable phone camera or a DSC (digital still camera). It can be classified as a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, depending upon method used to make the same and its application.
A color photographing part for a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor includes color filters each having additive mixing primary color filter segments of red, green, and blue, and the colors are separated.
A recent color filter embodied in the color photographing part has a pattern size of 2 μm or less, which is in a range of 1/100th to 1/200th that of the conventional color filter pattern for the LCD. Accordingly, increased resolution and decreased pattern residues are important factors to consider when determining the performance of a device.
It is believed that the kind and composition ratio of a photoinitiator, a monomer, and a binder and the pigment dispersion solution determine whether the resolution is increased and the pattern residues are decreased. Furthermore, in order to provide a fine pattern, the pigment dispersion solution should be prepared to have a small particle diameter and a composition that does not leave pattern residues when developing an image. In order to decrease the dispersing particle diameter of the pigment dispersion solution, the pigment should have a small primary particle diameter, and the kind and amount of a dispersing agent should be considered.
Recently-developed pigments for electronic materials have a primary particle diameter of around 50 nm to reduce the size of the particles after dispersion. In the case of a dispersing agent, it is possible to maintain dispersion by introducing a functional group that is capable of adhering to the surface of a pigment to provide a steric hindrance effect between the pigment particles and to leave a certain gap between them. The dispersing agent may include resins that are capable of providing enough steric hindrance, for example polyesters, acrylic resins, modified urethane resins, polyesters, and the like.
It is possible to provide a fine dispersion by using a dispersing agent that is capable of adhering to the pigment having a small particle diameter and providing the steric hindrance between particles so that the pigment is sufficiently dispersed. If the pigment dispersion solution further includes a dispersing agent that is capable of decreasing pattern residues when developing images, the resist composition for a color filter including the pigment dispersion solution may achieve a fine pattern.